R. L. Stearns

Experimental observation of the Σ hypernuclei, Σ6H and Σ16C

Abstract The hypernuclei Σ 6 H and Σ 16 C were observed by the (K − , π + ) reaction on targets of 6 Li and liquid O, respectively, at 713 MeV/ c incident K − momentum. Structure is seen in Σ 6 H which may be interpreted in terms of particle-hole excitations similar to the previously observed states in Λ 6 Li. The inablitity to resolve individual Σ hypernuclear levels in Σ 16 C, due in part to the excitation of non-coherent states as a result of the large momentum transfer of about 130 MeV/ c , precludes the extraction of the Σ-nucleus spin-orbit potential strength. The Σ-nucleus well depth appears to be 7 to 10 MeV less than that for the Λ.

States of 12ΛC formed in the reaction 12C(K−, π−)☆

Abstract States of 12 Λ C formed in the (K − , π − ) reaction have been studied for momentum transfers up to 260 MeV/ c , using an incident K − beam of 800 MeV/ c momentum. The angular distributions for the g.s. and for a peak at 11 meV have been measured between 0° and 19° in the laboratory. Limits on the splitting of the 11 MeV peak and on the formation of low-lying excited states are given.

States of

Abstract States of 12 Λ C formed in the (K − , π − ) reaction have been studied for momentum transfers up to 260 MeV/ c , using an incident K − beam of 800 MeV/ c momentum. The angular distributions for the g.s. and for a peak at 11 meV have been measured between 0° and 19° in the laboratory. Limits on the splitting of the 11 MeV peak and on the formation of low-lying excited states are given.

^{12}

Abstract The spectroscopy of hypernuclei across a wide range of mass number has been studies by the associated production (π+, K+) technique. The energies of Λ single particle states in the s, p, d, and f shells have been determinedas a function of A. It is demonstrated that the (π+, K+) reaction is the method of choice for studying Λ-bound levels of hypernuclei.

C (

Abstract The study of the K+ total cross sections on a wide range of nuclei has revealed important modifications of the free-space K+-nucleon interaction when the nucleon is embedded in a nucleus. Data indicating such an effect were first obtained in a comparison of the total cross sections on carbon and deuterium. In this letter we report new measurements on 6Li, silicon, and calcium, and demonstrate that the previously reported modifications occur quite generally.

\Lambda

We measured the lifetime and the mesonic and non-mesonic decay rates of the 4He-Lambda hypernucleus. The hypernuclei were created using a 750 MeV/c momentum K- beam on a liquid 4He target by the reaction 4He(K-,pi-)4He-Lambda. The 4He-Lambda lifetime was directly measured using protons from Lambda p -> n p non-mesonic decay (also referred to as proton-stimulated decay) and was found to have a value of tau = 245 +/- 24 ps. The mesonic decay rates were determined from the observed numbers of pi-s and pi0s as Gamma_pi-/Gamma_tot = 0.270 +/- 0.024 and Gamma_pi0/Gamma_tot = 0.564 +/- 0.036, respectively, and the values of the proton- and neutron-stimulated decay rates were extracted as Gamma_p/Gamma_tot = 0.169 +/- 0.019 and Gamma_n/Gamma_tot <= 0.032 (95% CL), respectively. The effects of final-state interactions and possible 3-body Lambda N N decay contributions were studied in the context of a simple model of nucleon-stimulated decay. Nucleon-nucleon coincidence events were observed and were used in the determination of the non-mesonic branching fractions. The implications of the results of this analysis were considered for the empirical Delta I = 1/2 rule and the decay rates of the 4H-Lambda hypernucleus.

) Formed in the Reaction

A review is made of those past, present, and planned experiments at the AGS whose primary purpose is to determine whether the H‐dibaryon exists. Preliminary results are given for experiment E813, based on partially‐completed analysis.

^{12}

A survey of quasi-elastic scattering of 800 MeV protons was carried out at LAMPF using the high resolution spectrometer, and targets of /sup 6/Li, Li, /sup 12/C, /sup 27/Al, /sup 40/Ca, /sup 51/V, /sup 90/Zr and Pb. Measurements were made at angles of 5, 7, 9, 11, 13, 15, 25, and 30/sup 0/. Absolute cross sections were obtained using known (p,p) elastic cross sections. The momentum spectra were taken from the elastic region to well beyond the quasielastic peak. The variation in peak cross section and the FWHM of the peaks with mass number is reported. Evidence is presented for the quasielastic scattering of protons from clusters of mass 4 in the nucleus. 2 references.

C (

We measured the lifetime and the mesonic and nonmesonic decay rates of the {sub {lambda}}{sup 4}He hypernucleus. The hypernuclei were created using a 750 MeV/c momentum K{sup -} beam on a liquid {sup 4}He target by the reaction {sup 4}He (K{sup -},{pi}{sup -}){sub {lambda}}{sup 4}He. The {sub {lambda}}{sup 4}He lifetime was directly measured using protons from {lambda}p{yields}np nonmesonic decay (also referred to as proton-stimulated decay) and was found to have a value of {tau}=245{+-}24 ps. The mesonic decay rates were determined from the observed numbers of {pi}{sup -}s and {pi}{sup circle}s as {gamma}{sub {pi}{sup -}}/{gamma}{sub tot}=0.270{+-}0.024 and {gamma}{sub {pi}}/{gamma}{sub tot}=0.564{+-}0.036, respectively, and the values of the proton- and neutron-stimulated decay rates were extracted as {gamma}{sub p}/{gamma}{sub tot}=0.169{+-}0.019 and {gamma}{sub n}/{gamma}{sub tot}{<=}0.032 (95% CL), respectively. The effects of final-state interactions and possible three-body {lambda}NN decay contributions were studied in the context of a simple model of nucleon-stimulated decay. Nucleon-nucleon coincidence events were observed and were used in the determination of the nonmesonic branching fractions. The implications of the results of this analysis were considered for the empirical {delta}I=(1/2) rule and the decay rates of the {sub {lambda}}{sup 4}H hypernucleus.

K^-

We measured the lifetime and the mesonic and non-mesonic decay rates of the 4He-Lambda hypernucleus. The hypernuclei were created using a 750 MeV/c momentum K- beam on a liquid 4He target by the reaction 4He(K-,pi-)4He-Lambda. The 4He-Lambda lifetime was directly measured using protons from Lambda p -> n p non-mesonic decay (also referred to as proton-stimulated decay) and was found to have a value of tau = 245 +/- 24 ps. The mesonic decay rates were determined from the observed numbers of pi-s and pi0s as Gamma_pi-/Gamma_tot = 0.270 +/- 0.024 and Gamma_pi0/Gamma_tot = 0.564 +/- 0.036, respectively, and the values of the proton- and neutron-stimulated decay rates were extracted as Gamma_p/Gamma_tot = 0.169 +/- 0.019 and Gamma_n/Gamma_tot <= 0.032 (95% CL), respectively. The effects of final-state interactions and possible 3-body Lambda N N decay contributions were studied in the context of a simple model of nucleon-stimulated decay. Nucleon-nucleon coincidence events were observed and were used in the determination of the non-mesonic branching fractions. The implications of the results of this analysis were considered for the empirical Delta I = 1/2 rule and the decay rates of the 4H-Lambda hypernucleus.